Agreed--conference dress can run the gamut from super formal to super casual--all at the same event. I usually try for something slightly up from business casual--a nice skirt and top, but nothing over done. The only time that led me astray was at a conference where everyone else--EVERYONE else was in blue jeans. It was a small conference and I felt hideously out of place, but there was nothing to be done. In the end it turned out to be the best conference I have been at, and the fact of what anyone was wearing became very secondary as we all enjoyed great discussions over dinner and wine and beer!